1. Field of the Invention
The present invention relates generally to optics used with optical heads and more particularly to offset optics used with magneto-optical heads.
2. Background Art
Winchester magnetic hard disk technology is influenced by a number of constraints, including, constraints imposed by flying magnetic head design. A typical prior art magnetic flying head includes a slider element and a magnetic read/write element and is coupled to a rotary actuator magnet and coil assembly by a suspension and actuator arm so as to be positioned over a surface of a spinning magnetic disk. In operation, lift forces are generated by aerodynamic interactions between the flying head and the spinning magnetic disk. The lift forces are opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk.
Flying head designs have been proposed for use with magneto-optical (MO) storage technology. One motivation for using magneto-optical technology stems from the availability of high areal density magneto-optical storage disks (e.g., 3.5 gigabytes per square inch for magneto-optical storage). However, despite the historically higher areal storage density available for use with magneto-optical disks drives, the prior art MO disk drive volumetric storage capacity has generally not kept pace with the volumetric storage capacity of magnetic disk drives. One limiting factor has been the physical size of the head necessary to hold the optical elements required for accessing magneto-optical information. Magneto-optical information access requires the use of polarized laser light for reading and writing information on an MO disk. In the case of reading information, MO technology makes use of a magneto-optical effect ("Kerr" effect) to detect a modulation of polarization rotation imposed on a linearly polarized incident laser beam by a recorded surface. The polarization rotation (representing the information stored at recorded marks on the recorded surface or in the edges of the recorded marks) is embodied in a reflection of the linearly polarized laser beam and is converted by optics and electronics for readout.
Various MO flying head designs incorporating MO technology are described in U.S. Pat. No. 5,295,122 by Murakami, including: use of free-space alignment of a laser beam with a dynamically moving target and a number of different configurations of the magnetic and optical elements required for detection of the magneto-optical Kerr effect. Accordingly, the physical size of the prior art MO flying heads limits the spacing between magneto-optical disks to a finite minimum value. Consequently, because the volume available in standard height disk drives is limited, magneto-optical disk drives for use with magneto-optical flying heads have generally not been available as high capacity commercial products. Also, the larger the size and the greater the number and mass of the optical elements used to access information in prior art MO data storage and retrieval systems, the slower the speed at which the information may be accessed, the lower the tracking bandwidth becomes, and the lower the track density that may be read or written.
What is needed, therefore, is an apparatus and method that improves upon the prior art head designs. Compared to the prior art, the head should improve access to the high areal storage density of storage media, reduce the head weight and size, improve disk access time, require fewer components, and increase the number of storage disks that may be operated within a given volume.